1. Field of the Invention
The present invention relates to a suction device (hereinafter also referred to as "suction gun") for drawing and holding a yarn by pressurized liquid such as pressurized water, thereby to thread the yarn to a desired position.
2. Description of the Prior Art
It is well known in the art that a movable suction gun for drawing and holding a running yarn is employed in order to thread the yarn to a desired apparatus such as a godet roller, a bobbin of a winder or a yarn guide. In such a suction gun, pressurized air or pressurized liquid is employed as actuating fluid for drawing the yarn.
A preferable type of suction gun employing pressurized water as actuating fluid is disclosed in U.S. Pat. No. 4,666,590, which comprises first and second injection nozzles (suction nozzles). The first injection nozzle is provided oppositely to an inlet port of a pressurized liquid exhaust pipe, so that the yarn is thrust into the interior of the pressurized liquid exhaust pipe (yarn guide pipe) by injection force of the pressurized water injected from the first injection nozzle. An internal space of the pressurized liquid exhaust pipe defines a pressurized liquid exhaust passage. The second injection nozzle is provided in the upstream portion of the pressurized liquid exhaust passage, to obliquely inject pressurized water into the pressurized liquid exhaust passage. The yarn in the pressurized liquid exhaust passage is sucked and drawn by injection force of the pressurized water from the second injection nozzle, to be discharged from the suction gun with the pressurized water.
In such a two-stage injection type suction gun, an injection nozzle having a plurality of jets is employed as the second injection nozzle. In such prior art, the plurality of jets are so directed that the axes thereof intersect with each other at a single point on the axis of a through hole forming a part of the pressurized liquid exhaust passage, which is identical to an axis of the first injection nozzle. Therefore, the pressurized water introduced into the pressurized liquid exhaust pipe by the first injection nozzle is subjected to interference by the pressurized water from the second injection nozzle, and the yarn sucking force or tension in the suction gun is remarkably weakened. As the result, a large amount of pressurized water must be supplied in order to apply sufficient suction force to the yarn, whereby the cost required for the water supply is increased.